The level of shooting accuracy desired by bow hunters and competition archers exceeds that readily achievable without the use of a sighting device such a simple pin sight or an optical sight capable of magnification. Such sighting devices are typically used in conjunction with a support bracket attached to the bow riser to precisely position the sight between the archer's eye and the target. Conventional bow sight supports are deficient because they are not sufficiently adjustable to maintain the sight within the archer's line of sight to the target as the archer raises or lowers the bow relative to horizontal, depending upon the distance to the target, to provide an arrow trajectory which terminates at the target. Instead, conventional sight supports are typically fixed to the bow riser and provide a pivotal adjustment of the sight so that when the bow is raised, for example, to provide the arrow trajectory required for a distant target, the sight may be tilted downwardly relative to horizontal toward the target. This sight positioning requires an adjustment in the position of the archer's eye relative to the position of the anchor point of the string when fully drawn (i.e., an adjustment in peep height) so that the archer's line of sight to the target passes through the bow sight to thereby realize the aiming benefits of the sight. Since accurate shooting requires a repeatable draw and shooting stance, any adjustments in peep height are considered undesirable.
Other conventional sight supports provide arcuate adjustment of the sight along a path curved or bowed outwardly from the archer's eye to minimize the peep height adjustment required for a particular target. Nonetheless, since this arcuate adjustment path does not precisely correspond to the arc along which the bow is positioned to provide the desired arrow trajectory, some peep height adjustment is still required. Furthermore, the amount of peep height adjustment mounting depends upon the particular archer's draw length (i.e., the approximate distance between the archer's grip on the riser and the archer's anchor point). An archer with a long draw length positions the bow riser for various arrow trajectories along an arc which is more gradual than the aiming arc of an archer with a short draw length. Since the arcuate adjustment path of conventional supports is not adjustable to correspond to bow adjustment paths, the more the archer's bow adjustment path differs from the arcuate path provided by such sight supports, the greater the required peep height adjustment.
Also, conventional sight supports require the use of shims to compensate for the twisting or cantering of the bow riser which occurs under full draw conditions (i.e., when the bow string is drawn). Since the sight support is mounted to the riser, as the riser canters about its vertical axis, the sight also rotates. Thus, the sight must be positioned in a skewed orientation relative to the line of sight to the target under relaxed conditions (i.e., when the string is not drawn) so that it will rotate into alignment with the line of sight under full drawn conditions. Heretofore, shims have been wedged between the riser and the sight support to position the support at an angle to compensate for the riser canter. Such shims vibrate loose and are easy to lose and difficult to install. Additionally, since the degree of canter depends upon the flexibility of the riser and bow limbs, the action of the cams, and the characteristics of the string system, the cumbersome process of shim adjustment must be repeated for each variation in bow setup.